1. Field of the Invention
The present invention relates to aircraft warning systems and more particularly to a warning system and method that monitors aircraft sensor data and provides warnings of a potential ground collision based on projected flight path analysis. The invention further relates to a method and apparatus configured for integration into advanced electronic data systems for accumulating available flight data and projecting a probable flight path above terrain.
2. Background of the Related Art
It is well understood in aviation technology and design that the inability of a pilot to know the full condition of an aircraft, or to perceive imminent danger, results in many aircraft crashes. Such is the case in those crashes occurring in fog or other bad weather or those where instrument indications were not sufficient to show an obstruction or other aircraft before it was too late. Another example is the sudden alteration of flight characteristics due to aircraft damage which cannot be rapidly understood and definitely not observed from the pilot's vantage point. Therefore, appropriate corrective measures are often not taken before it is too late. In addition, airframe or control system failures have increasingly significant impacts on aircraft performance. The advanced technology control systems on which many new commercial and military aircraft pilots must rely are so critical to the operation of the aircraft that any failure during aircraft maneuvering can lead to loss of control.
However, even in "good" weather, with external influences minimized, copious instrumentation, and full pilot control, crashes still occur. The "controlled flight into terrain" type of crash results from a variety of factors including pilot error as a result of fatigue or distraction, and instrumentation error.
In order to help counter some of these problems, a variety of altitude and collision avoidance instruments or warning devices have been developed. Such instruments generally monitor current aircraft altitude above local terrain and downward velocity or "sink rate" to determine if the aircraft is dropping below a predetermined safe altitude limit. These systems generally rely on radar altimeters to establish current altitude above terrain and vertical velocity or sink rate. The sink rate represents a ground closure rate which has a corresponding "safe" altitude or ground separation distance above which it is assumed the aircraft can easily maneuver to avoid ground collision. When an aircraft drops below this altitude an alarm is sounded to cause the pilot to change the aircraft flight configuration and thereby alter the ground closure rate. However, prior art warning systems have tended to provide "false" warnings under conditions such as short periods of negative upward acceleration on take-off where pilots knew there was no real danger. When these systems are made very sensitive, they tend to provide false warnings over highly variable terrain. If the warning system provides too many "false" warnings it is ignored by flight crew or pilots and loses its value.
Aircraft used in commercial passenger and freight transport do not use highly complex or demanding maneuvering patterns. Nevertheless, highly crowded flight paths and air traffic corridors place a severe demand on pilot attention. Pilots often need to rely on warning systems to help them react to problems that cannot focus on. It is imperative that such as system have pilot confidence. A system that more accurately accounts for aircraft performance and capability to recover from a given ground closure or low altitude scenario would help increase pilot trust and likelihood of use.
For military aircraft the operating problems or considerations are more stringent in terms of aircraft performance during maneuvering. In an environment where the pilot is keeping track of other aircraft and/or undertaking a series of complex or extreme maneuvers it becomes increasingly difficult to observe terrain closure. While there is generally an abundance of instrumentation on-board, this presents more of an over-information distraction than an aid. It is not possible for a pilot to constantly monitor all flight instrumentation nor adequately comprehend the information provided under combat conditions. The pilot needs a quick and direct warning of ground closure.
In addition, stealth flying and other advanced combat type maneuvers often call for a pilot to "over-fly" his instruments, that is, fly the aircraft in configurations or at altitudes that are considered dangerous according to conventional instrumentation but from which highly maneuverable aircraft with high power engines have a margin for recovery. In this situation pilots begin to rely totally on the feel of the aircraft and a sense of direction, since instrumentation based on current readings does not respond fast enough to warn of rapid changes.
Unfortunately, it is extremely difficult if not impossible for pilots to adequately judge the recovery capability or margin of safety for advanced technology aircraft in high stress maneuvering situations since these aircraft have very complex control systems and functions. Also, altitude is affected by various aspects of aircraft maneuvering including climbing or diving, rolling, and banking in addition to the vertical velocity and acceleration. In addition, changes in airframe loading and weight contribute in a manner unpredictable or not always observable to a pilot attending to target tracking during maneuvering. To hold the aircraft at the maximum maneuvering limits yet provide a margin of safety the pilot needs help. However, current warning systems react too slowly and rely on simple "current" altitude readings which do not adequately predict flight path for a maneuvering aircraft at high speeds. The current warning indicators have failed to recognize or treat any interrelationship between vertical velocity, maneuvering, or other aircraft flight characteristics.
What is needed then is a method or apparatus for providing improved high speed response in a warning system that presents brief and useful information and also commands pilot attention in high activity situations. A warning system is also desired that minimizes false alarms.